The present invention relates to a ceramic packaged semiconductor device with a semiconductor element contained in a hollow package of ceramics.
Semiconductor devices with a semiconductor element such as IC, LSI, etc. contained in a package of ceramics having an inside space and with lead conductors introduced into the package, the semiconductor element and lead conductors being connected with one another by bonding wires in the inside space of the package, are widely used. Similarly, resin-sealed semiconductor devices are also commonly used. A significant problem with such package type semiconductor devices, however, is poor heat dissipation due to the use of the package. Obviously, the poor heat dissipation is a great obstacle to an attempt to make a semiconductor device with a larger capacity, a higher integration density and a smaller size. Thus, a material with a lower heat resistance is required for an insulating substrate for providing a semiconductor element in a ceramics package. Besides, a material for the insulating substrate must satisfy (1) a higher electical insulation, (2) a substantially equal coefficient of thermal expansion to that of silicon, and (3) a higher mechanical strength. Sintered alumina is now used as an insulating substrate which can meet these requirements to some extent. From the standpoint of the thermal resistance, however sintered alumina having a low thermal conductivity, such as 0.05 cal/sec.cm..degree.C., is not regarded as a preferable material for the insulating substrate for the semiconductor device, when an attempt to make the integration density higher and the capacity larger is taken into account.
As an approach for improving the heat dissipation characteristic of the ceramic packaged semiconductor device, such a structure as shown in FIG. 1 is proposed, in which a semiconductor element 31 is mounted on the top of a stud 32 of copper which extends through an insulating substrate 301 to the exterior of a ceramic package denoted by numeral 30. In this figure, reference numeral 33 denotes a supporting plate of molybdenum interposed between the semiconductor element 31 and the copper stud 32 to serve for mitigating thermal stress which is possibly produced due to a difference in the coefficient of thermal expansion between the semiconductor element 31 and the stud 32. Reference numeral 34 denotes lead conductors secured to the insulation substrate 301. Numeral 35 denotes bonding wires for connecting, respectively, the inner ends of the lead conductors 34 to the semiconductor element within the cavity of the package 30. Numeral 302 denotes a cap member bonded to the insulating substrate 301 in a hermetical manner and constituting a part of the package 30. Finally, reference numeral 36 denotes a cooling fin mounted on and around the copper stud 32. With this structure, all the heat conducting paths extending from the semiconductor element 31 to the cooling fin 36 are provided by metals having a high thermal conductivity, whereby a semiconductor device having an improved heat dissipation characteristic due to the reduced overall thermal resistance can be obtained. However, the semiconductor device shown in FIG. 1 suffers disadvantages in that an increased number of manufacturing steps are required because of a complicated structure requiring an increased number of components, the weight of the semiconductor device is increased due to the use of heavy components such as those of molybdenum and others, and a troublesome procedure is required for mounting a printed circuit or the like onto the device.